Dial plate for solar battery powered watch

ABSTRACT

The dial plate according to the present invention comprises a substrate formed of a ceramic material and a colored coating layer formed on the substrate. And, the colored coating layer is characterized by having a colored layer formed of a ceramic paint containing a metal compound as a principal component. The substrate formed of a ceramic material is porous; and hence, diffuses incident light to conceal a solar battery placed on the backside from view. Since the colored layer is formed of a ceramic paint containing a metal compound as a principal component, it is easy to firmly attach it to the substrate formed of a ceramic material and it is capable of forming various colors corresponding to the types of metal compounds applied.

TECHNICAL FIELD

The present invention relates to a dial for a solar battery poweredwatch activated by a solar battery energy.

BACKGROUND ART

Demand for watches which are virtually permanently usable in differentcountries where different types of batteries are used has progressivelybeen increasing with the recent development of internationaldistribution of watches. The market for solar battery powered watches,which are capable of meeting the aforesaid requirement, has rapidlyexpanded. Solar battery powered watches have attracted attention fromthe view point of worldwide environmental protection because the solarbatteries of solar battery powered watches need not be replaced with newones and solar battery powered watches will not cause environmentalcontamination due to the disposal of spent batteries.

Generally, a solar battery powered watch employs the solar batteryitself as the dial plate and hence the surface of the dial plate assumesa dark purple appearance unique to the solar battery, which spoils theornamental value of the watch and, consequently, places significantrestriction on the design of the dial plate.

Thus, a dial is desired which enables the color thereof to bediversified so as to satisfy the various tastes of purchasers.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the foregoingcircumstances and it is therefore an object of the present invention toprovide a dial plate for a solar battery powered watch that conceals thecolor and electrode pattern of the solar battery from view whiletransmitting sufficient quantity of light to the solar battery, andwhich facilitates diversification of the color thereof.

With the forgoing object in view, the present invention provides a dialplate for a solar battery powered watch provided with a solar battery,to be disposed on the front side of the solar battery, comprising asubstrate formed of a ceramic material, and a colored coating layerformed on a front surface of the substrate, wherein the colored coatinglayer has a colored layer formed of a ceramic paint containing a metalcompound as a principal component.

Since the ceramic material per se is normally completely transparentrelative to light and cannot absorb the incident light, and it is formedof a polycrystalline material and has many crystal grains, the substratemade of the ceramic material functions to irregularly reflect anddiffuse the incident light. A part of the light incident on the dialplate does not transmit through the dial plate but irradiates from thesurface of the dial plate owing to the diffusing function or operationand almost all the remaining incident light transmits through the dialplate and reaches the solar battery provided on the back surface of thedial plate.

The light reaching the solar battery is reflected therefrom, and a partof the light is again incident on the back surface of the dial plate andis irradiated from the front surface of the dial plate while it issubjected to the diffusing operation. Accordingly, the color andelectrode pattern of the solar battery can be almost concealed from theviewer of the dial plate since the light irradiated from the frontsurface of the dial plate without transmitting through the dial plateand the light which is reflected from the solar battery and isirradiated from the front surface of the dial plate while it issubjected to the diffusing operation on the dial plate are overlaid uponeach other.

Since the colored layer is disposed on the surface of the substrate,forming dial plates in various colors is possible. Since the coloredlayer is formed of a ceramic paint containing a metal compound as aprincipal component, it is firmly attachable to the substrate formed ofa ceramic material, and various colors can be formed corresponding tothe kind of a metal compound.

Forming an intermediate layer between the colored layer and thesubstrate, and forming the foregoing coating layer by the intermediatelayer and colored layer are also possible. This intermediate layer canbe formed of a glass film or an oxide film.

Since the intermediate layer is formed, keeping the ceramic paint fromsoaking into the base plate, reducing blurring in sight, and presentinga sharp color tone becomes possible.

Further, a surface layer formed of a glass film or oxide film on thesurface of the colored layer may be formed. Forming the surface layerenables the colored layer to be protected and the dial surface to bemade glossy.

Furthermore, smoothing by lapping the surface of the substrate andsurface layer will restrict the irregular reflection of light on thesurface and enhance the transmittance of light.

On the contrary, roughening the surface of the substrate and surfacelayer will strengthen the irregular reflection of light on the surfaceand produce a soft tone dial.

The present invention also provides a dial plate for a solar batterypowered watch provided with a solar battery, to be disposed on a frontside of the solar battery, comprising a substrate formed of a ceramicmaterial, and a colored coating layer formed on a front surface of thesubstrate, wherein the colored coating layer is a mixed colored layerformed by a coloring material mixed with one of a glass material or anoxide material and a ceramic paint containing a metal compound as theprincipal component.

The mixed colored layer is formed of the coloring material mixed with aglass material or oxide material, and these materials by their naturerestrict the ceramic paint from soaking into the substrate; thus makingthe color tone of the dial plate glossy as well as deep.

And, the coating layer may be formed by a surface layer formed of theglass film or oxide film on the surface of the mixed colored layer andthe mixed colored layer.

The surface layer functions to make the surface of the dial plate glossyas well as protecting the mixed colored layer.

In the constitutions mentioned above, smoothing by lapping the front orrear surface of the dial plate, the surface of the mixed colored layer,or the surface of the surface layer will restrict the irregularreflection of light on said surface and enhance the transmittance oflight.

On the contrary, roughening the surface of the substrate, the surface ofthe mixed colored layer, or the surface of the surface layer willstrengthen the irregular reflection of light and present a soft tone tothe dial plate.

The present invention also provides a dial plate for a solar batterypowered watch provided with a solar battery, disposed on the front sideof the solar battery, and having predetermined additive functionalregions and a non-additive functional region on the front surfacethereof, comprising a substrate which is formed of a ceramic materialand provided with the additive and non-additive functional regions, onthe surface of the dial plate, wherein the additive and non-additivefunctional regions differ in thickness from each other.

Since the additive functional and non-additive functional region areformed in different thicknesses, the transmittance and the diffusioncoefficient of light are different in each of these two types of region.Consequently, these regions each appear in different color tones.

A colored layer of a coloring material containing at least a ceramicpaint containing a metal compound as a principal component may be formedon at least either the additive functional regions or non-additivefunctional region.

When thus formed, the additive functional regions and the non-additivefunctional region assume different color tones, respectively, accordingto the color of the colored layer.

Further, forming the intermediate layer of a glass film or an oxide filmbetween the colored layer and the substrate will keep the ceramic paintfrom soaking into the substrate and avoid blurring in sight, producing adeep tone.

Furthermore, forming the surface layer of a glass film or an oxide filmon the surface of the colored layer will make the dial surface glossy aswell as protect the colored layer.

The present invention further provides a dial plate for a solar batterypowered watch provided with a solar battery, disposed on the front sideof the solar battery, and having predetermined additive functionalregions and a non-additive functional region on a front surface thereof,comprising a substrate which is formed of a ceramic material andprovided with the additive and non-additive functional regions, whereinon at least one of the additive or non-additive regions the coloredlayer is formed of a coloring material containing at least a ceramicpaint containing a metal compound as a principal component.

Thus, forming the colored layer will cause the additive functional andnon-additive functional regions to appear in different color tones.

Forming the intermediate layer of a glass film or an oxide film betweenthe colored layer and the substrate will hereat also keep the ceramicpaint from soaking into the substrate and avoid blurring in sight,producing a deep color tone.

Furthermore, forming the surface layer of a glass film or an oxide filmon the surface of the colored layer will make the surface of the dialplate glossy as well as protect the colored layer.

It is preferable to adjust the thickness of the substrate, coloredlayer, mixed colored layer, intermediate layer, or the surface layerdescribed above, in consideration for the transmittance of light, thatis, to adjust the transmittance of these layers so that a solar batteryplaced on the rear side of the dial can absorb the energy of light fordriving the watch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the first embodiment of thepresent invention.

FIG. 2 is a plan view of the dial plate of FIG. 1.

FIG. 3 is a sectional view showing the constitution of a solar batterypowered watch in which a dial plate relating to the present invention isincorporated.

FIG. 4 is a sectional view showing the modified embodiment of a dialplate for a solar battery powered watch relating to the firstembodiment.

FIG. 5 is a sectional view showing another modified embodiment of a dialplate for a solar battery powered watch relating to the firstembodiment.

FIG. 6 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the second embodiment of thepresent invention.

FIG. 7 is a sectional view showing the modified embodiment of a dialplate for a solar battery powered watch relating to the secondembodiment.

FIG. 8 is a plan view showing the constitution of a dial plate for asolar battery powered watch relating to the third embodiment of thepresent invention.

FIG. 9 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the third embodiment of thepresent invention.

FIG. 10 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the fourth embodiment of thepresent invention.

FIG. 11 is a sectional view showing the constitution of the fourthembodiment comprising an intermediate layer and colored layer.

FIG. 12 is a sectional view showing the constitution of the fourthembodiment comprising a colored layer and surface layer.

FIG. 13 is a sectional view showing the constitution of the fourthembodiment comprising an intermediate layer, colored layer, and surfacelayer.

FIG. 14 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the fifth embodiment of thepresent invention.

FIG. 15 is a sectional view showing the constitution of the fifthembodiment comprising an intermediate layer and colored layer.

FIG. 16 is a sectional view showing the constitution of the fifthembodiment comprising a colored layer and surface layer.

FIG. 17 is a sectional view showing the constitution of the fifthembodiment comprising an intermediate layer, colored layer, and surfacelayer.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be describedhereinafter with reference to the accompanying drawings, in order thatthe present invention will be detailed in the content.

First Embodiment

FIG. 1 is a sectional view showing the constitution of a dial plate fora solar battery powered watch relating to the first embodiment of thepresent invention, FIG. 2 is a plan view of the dial plate of FIG. 1.

And, FIG. 3 is a sectional view showing the constitution of a solarbattery powered watch in which a dial relating to the present inventincorporated.

First, the constitution of the solar battery powered watch will bedescribed with reference mainly to FIG. 3. It is noted that the presentinvention is not limited in its practical application to the dial plateincorporated into the solar battery powered watch shown in FIG. 3.

As shown in FIG. 3, a movement 3 for turning hands 2 is contained in acase 1 having a front and a back open end. The movement 3 comprises acapacitor for storing energy generated by a solar battery 4, which willbe described later, a quartz oscillator as the time base, asemiconductor integrated circuit that generates drive pulses synchronouswith the generating frequency of the quartz oscillator, a stepping motordriven by the drive pulses to drive the hands 2 every one second, awheel train mechanism for transmitting the driving force of the steppingmotor to the hands 2, and the like.

An annular inner frame 5 formed of a resin is placed in the case 1 so asto surround the movement 3. A stepped part 5a to seat the dial plate 6thereon is formed in one end of the inner frame 5, and the dial plate 6is fitted in the stepped part 5a.

The depth of the stepped part 5a is substantially equal to the thicknessof the dial plate 6, so that the surface of the dial plate 6 as fittedin the stepped part 5a is substantially flush with the end surface ofthe inner frame 5.

Formed in the circumferential surface of the stepped part of the innerframe 5 are, for example, two recesses (not illustrated). The dial plate6 is provided with, for example, two projections 6a (FIG. 2) whichengage with the recesses formed in the circumferential surface of thestepped part 5a to position the dial plate 6.

A solar battery 4 is installed on the rear side of the dial plate 6. Thesolar battery 4 functions to convert light energy into electric energy,as is well known.

And, a cover glass 8 is fitted in inside a front opening part of thecase 1 through a second packing member 7 made of a resin or the like. Onthe other hand, a rear lid 10 is fitted in on a rear opening part of thecase 1 through a first packing member 9 made of a rubber or the like.Fitting the cover glass 8 and the rear lid 10 in on the case 1 will keepthe inside of the case 1 airtight and prevent dust, moisture,contaminants and the like from entering inside.

Further, an annular member 11 called a spacer is installed between thedial plate 6 and the cover glass 8. Mirror polishing is performed on thesurface of the annular member 11, which serves to decorate the peripheryof the dial plate 6.

As shown in FIG. 3, the inner frame 5 holding the movement 3, the solarbattery 4, and the dial plate 6 is placed in the case 1. These membersheld by the inner frame 5 are clamped by the annular part 11 placed onthe front side and the rear lid 10 placed on the rear side, thuspreventing looseness.

A throughhole 6b (FIG. 2) is formed at the center of the dial plate 6,so that a shaft 3a for driving the hands can be projected through thecenter of the movement 3 to the surface side of the dial plate 6. Aroundthe shaft 3a, a hand 2 including an hour hand, minute hand, and secondhand are attached.

And, characters including a time scale and brand name, and other symbolsare indicated on the surface of the dial plate 6. Further, an indicatingwindow 6c for the date and the day of the week is formed on the dialplate (FIG. 2).

Next, the method of manufacturing the solar battery 4 will be described.

First, Kovar which is an alloy made of iron, nickel, and cobalt ispressed so that a supporting base plate is formed for the solar battery4.

Two positioning pins (not illustrated) are attached, for example, byadhesive, or by spot welding on the rear side of the supporting baseplate.

These positioning pins are to position and fix the solar battery 4 onthe surface side of the movement 3; in assembling a watch, they areloosely put in positioning holes (not illustrated) formed on themovement 3. The solar battery 4 can be adhered directly on the surfaceof the movement 3 without forming the positioning pins.

Next, a glass layer as an insulating film is formed on the surface ofthe supporting base plate. The coefficients of linear expansion of theKovar forming the supporting base plate and the glass layer are madevirtually equal, which protects the glass layer from being damaged bytemperature change.

The glass layer is formed in such a manner that a liquid glass film(SOG) is applied on the surface of the supporting base plate by therolling application method, and then is baked under the temperature of300° C. to 400° C. to evaporate the solvent contained in the appliedglass film. The thickness of the glass layer formed is, for instance, 1to 2 μm.

Next, a lower electrode (not illustrated) is formed on the surface ofthe glass layer by using a sputtering machine. The lower electrode isformed on an optional area on the surface with a thickness of about 1 μmby using aluminum containing silicon in 1% by weight (wt %).

Next, an antidiffusion layer made of chrome is formed with a thicknessof 100 nm on the upper surface of the lower electrode by using thesputtering machine. The antidiffusion layer functions to hinder thelower electrode and the semiconductor layer from diffusing with eachother. When the lower electrode is formed by a metal film of a highmelting point or an alloy film of a high-melting-point metal andsilicon, the antidiffusion layer can be omitted.

Further, in an optional area on the surface of the antidiffusion layer,a semiconductor layer made of a thin film non-crystalline silicon isformed which works as a solar battery.

An amorphous silicon layer, for example, can be applied for thenon-crystalline film. The conductive type of the semiconductor layer,for example, is made to be an n-i-p structure in that order from theside of the antidiffusion layer.

Next, in an optional area on the surface of the semiconductor layer, atransparent electrode film is formed using indium tin oxide (ITO) as anupper electrode.

Finally, a protective film is formed on the surface by an acrylic resinor epoxy resin having a transmittance of light of about 99%, thuscompleting fabrication of the solar battery 4.

Next, the constitution of the dial plate 6 relating to the firstembodiment will be described, mainly with reference to FIG. 1.

The dial plate 6 comprises a colored coating layer on the surface of thebase plate 61.

The dial plate 6 is disposed on the front side of the solar battery 4 asshown in FIG. 3 and has a function to conceal the solar battery 4 fromview, and another function contradictory to the previous function totransmit the light as much as possible so that the solar battery cansecure a sufficient amount of solar energy or electric power. Theadjustment of transmittance of light has very important meaning for thedial plate 6 of the solar battery.

For example, it is preferable that the dial plate 6 has a transmittanceof light capable of transmitting 1/4 or more of the irradiated light soas to secure sufficient electric power for the solar battery 4 and tokeep a steady driving of the watch. Further, it is preferable that thedial plate of a watch provided with an additive function such as anilluminating or alarming function which consumes much power has atransmittance of light capable of transmitting 1/3 or more of theirradiated light.

Meanwhile, it is preferable that the dial plate has a transmittance oflight capable of transmitting 2/3 or less of the irradiated light toconceal the solar battery 4 (particularly the color thereof) from view.Further, if the dial plate 6 has a light color, it is preferable thatthe dial plate has a transmittance of light capable of transmitting 1/2or less of the irradiated light so as to more securely conceal the solarbattery 4 having a dark color, such as dark violet.

In view of the security of the electric power and of the concealing ofthe solar battery 4, it is preferable that the transmittance of light ofthe dial plate 6 be adjusted.

A specific region of wavelength of the light incident on the dial plate6 is absorbed by the colored coating layer. Meanwhile, since the amountof electric power of the solar battery 4 is varied depending on theregion of wavelength of the incident light, it is useless if the dialplate transmits light in the region of wavelength which light does notcontribute to the generation of the electric power of the solar battery4. Accordingly, it is preferable that the transmittance of light of thedial plate 6 of the present invention be decided based on the light inthe region of wavelength contributing to the generation of the electricpower of the solar battery 4.

Accordingly, it is preferable that the transmittance of light of thedial plate 6 be decided based on the ratio between the amount ofelectric power of the solar battery 4 generated by the light irradiatedon the solar battery 4 in a state where the dial plate 6 is not insertedand that of the solar battery 4 generated by the light transmittedthrough the dial plate 6 in a state where the dial plate 6 is inserted.

The substrate 61 is made of a ceramic material having a thicknessranging from about 0.1 mm to 0.5 mm. The thickness of the substrate 61is properly adjusted considering the strength and the transmittance oflight. That is, the thickness of the substrate 61 is adjusted to keepthe strength capable of withstanding the usage of the dial plate of awatch and to secure a transmittance of light capable of transmittingabout 30 to 70% of the irradiated light considering the attenuation ofquantity of light transmitting through the colored coating layer.

The substrate 61 is formed of a ceramic material which contains, forinstance, alumina or zirconia as a principal component.

Light incident on the substrate 61 made of the ceramic material isreflected irregularly on the surface and in the inside of the substrate61, and a portion of incident light is reflected from the substrate 61.On the other hand, after irregularly reflecting inside the substrate 61,light transmitted through the substrate 61 reflects on the solar battery4, again reflects irregularly on and inside the substrate 61, and aportion thereof again transmits through the substrate 61. Through aprocess of reflection and transmission caused by a series of irregularreflections, the color of the solar battery 4 and the electrode patternis substantially concealed from view.

The colored coating layer is comprised of a colored layer 62 formed ofpaint (ceramic paint) for painting ceramics.

The ceramic paint contains a metal compound as a principal component,and is formed in such a manner that a metal oxide as the metal compoundis dispersed into water or oil and the viscosity thereof is adjusted byusing funori (liquid glue of a marine alga) or the like, or is a liquidpigment paint in which water-soluble metallic chloride as the metalcompound is dissolved into water. Different kinds of metal compound canbe used to assume different colors.

Using cobalt chloride or cobalt nitrate as the metal compound for theliquid pigment paint will produce a blue colored layer 62. Using ironchloride or iron sulfate will produce a yellow colored layer 62. Usingferric chloride or copper sulfate will produce a green colored layer 62.Using chromium sulfate or chromium nitrate will produce a brown coloredlayer 62. Using gold chloride will produce a pink colored layer 62.

Thus, selection of the kind of the metal compound will present variouscolors needed for designing the dial plate 6 for the watch.

Further, mixing several kinds of the metal compounds described above inan appropriate ratio will produce a colored layer 62 having varioustones.

Mixing, for instance, metal oxides of cobalt and chrome will produce agreen spectrum colored layer 62. Mixing metal oxides of cobalt andmanganese will produce a blue spectrum colored layer 62. Mixing metaloxides of gold and cobalt will produce a red-purple spectrum coloredlayer 62.

Furthermore, these paints are what is called an underglaze paint whichis usually processed under a baking temperature of 1100 to 1300° C.;however, adding a frit of lead derivatives will produce what is calledan overglaze paint which develops its color under a low bakingtemperature of 700 to 900° C.

Next, the method of manufacturing the dial plate 6 relating to the firstembodiment will be described by dividing it into the manufacturingmethod of the substrate 61 and the formation of the colored coatinglayer.

First, the method of manufacturing the substrate 61 will be described.

A ceramic material with a binder added is filled in into a metal mold.The metal mold forms its inner shape so as to form the external shape ofthe dial plate 6, the throughhole 6b, the indicating window 6c and thelike.

Alumina or zirconia with a grain diameter of about 0.3 μm is used forthe ceramic material. The binder is added in by about 3.0% to theceramic material. It is preferable to use alumina or zirconia having apurity of more than 99.9%. And, polyvinylalcohol (PVA), for example, isused for the binder.

A pressing treatment is executed by using a press machine on the metalmold in which the foregoing materials are filled in. The pressurethereat is about 1 ton/cm².

Next, a first baking treatment is executed to remove the binder added inthe ceramic material. The first baking treatment is conducted under thetemperature of about 1200 to 1400° C., taking about 120 minutes for thebaking time. The ambient atmosphere for the baking treatment is air.Since the first baking treatment removes the binder, the outsidedimension of the ceramic material becomes slightly smaller, however thethickness virtually does not change.

Next, a second baking treatment is executed. The second baking treatmentis conducted under a temperature (for example, 1500 to 1900° C.) wherethe sintering of the ceramic material is accelerated, taking about 300minutes for the baking time. The ambient atmosphere for the bakingtreatment is hydrogen gas. The second baking treatment advancescrystallization of the ceramic material so that the grain diameterbecomes larger than 0.3 μm.

Thus, as the grain diameter of the ceramic material enlarges, the areaof the crystal grain boundary in the substrate 61 reduces; consequently,irregular reflection on the surface of the crystal grain boundary isrestricted, which increases the transmittance for light.

After the second baking treatment is complete, the front and rearsurface of the substrate 61 are flattened by using a grinding machine.Diamond abrasive grains, for example, are used for the grinding machine.The thickness of the substrate 61 is made about 0.3 mm by this grinding.

Next, a third baking treatment is executed on the substrate 61. Thebaking temperature (for example, 1200 to 1400° C.) is lower than that ofthe second baking treatment. The third baking treatment is conducted inair, taking about 120 minutes for the baking time, to removecontamination attached on the surface of the substrate 61.

Next, a barrel polishing is executed on the substrate 61 by using abarrel machine. The barrel polishing is conducted by using, for example,copper (Cu) balls. This barrel polishing decreases the surface roughnessof the substrate 61, and still further increases the transmittance oflight of the substrate 61. And, the barrel polishing can remove burrsmade on the outer rim and the corner of the substrate 61, and can giveroundness on the corner.

Finally, a fourth baking treatment is executed on the base plate 61. Thebaking temperature thereat is comparable to that of the third bakingtreatment. The fourth baking treatment is conducted in air, taking about120 minutes for the baking time. This fourth baking treatment removescontamination attached on the surface of the substrate 61 to keep thesurface clean.

Provided that the substrate 61 can be firmed to be flat as well as sothat the dispersion of the thickness can be reduced by the pressingtreatment and the first and second baking treatment in the manufacturingprocess of the substrate 61 as described above, the grinding and thethird baking process may be omitted.

Instead of pressing in a metal mold the substrate 61 can also be made,for example, by pressing a green sheet, and thereafter by baking it. Andalso, the substrate 61 can be made with a powder injection molding, byconducting the baking treatment.

The surface of the base plate 61 may be made a smooth surface with asurface roughness of about 0.05 to 0.1 μm by lapping or the like. Thiswill restrict the irregular reflection of light on the surface thereof(finally, the interface with the colored layer 62) and enhance thetransmittance of light. Consequently, the quantity of light reaching thesolar battery 4 placed on the rear side of the dial plate 6 increases,so that the solar battery generates more electromotive force.

Lapping can be done by using diamond abrasive grains having a graindiameter of about 3 μm.

On the contrary, barrel or honing processing can roughen the surface ofthe substrate 61. In this case, the irregular reflection is strengthenedon the surface (finally, the interface with the colored layer 62) of thesubstrate 61, and the transmittance for light is decreased; however, theirregular reflection of light will present soft and warm color tones.

Next, the method of forming the colored coating layer will be described.

The colored layer 62 is formed on the surface of the substrate 61 madeof the ceramic material formed by the method described above. In thiscase, both the underglaze paint of a high temperature baking type andthe overglaze paint of a low temperature baking type can be used. Thecolored layer 62 is formed by using a ceramic paint of a desired color.The thickness of the colored layer 62 may be adjusted to about 5 μm to10 μm.

The ceramic paint forming the colored layer 62 is so adjusted that metaloxide such as cobalt oxide and water are mixed in the ratio of 8 to 2,and further an equal quantity (10) of glycerin is added to form themixture into a liquid state. Oil of balsam, turpentine, or lavender maybe used instead of water for a solvent.

The ceramic paint is applied on the surface of the substrate 61 by thescreen printing method, rolling application method, and manual operationby a writing brush or paint brush. And, using the screen printing methodthe ceramic paint is applied onto a transfer paper and dried, andthereafter, a covercoat is formed on the upper surface thereof. Next,the ceramic paint is transferred onto the covercoat, which is peeled offfrom the transfer paper so as to be transferred to the surface of thesubstrate 61; thus the colored layer 62 may be formed.

Afterward, a baking treatment is conducted under a temperature of 750°C. to 800° C., so that the colored layer 62 having a desired color canbe made on the surface of the substrate 61.

This baking treatment is executed in an atmosphere, for example, ofoxidation or reduction. The treatment in the atmosphere of oxidation orreduction develops different color tones even if the same ceramic paintis used. And, the color tone differs depending on the difference of thefilm thickness of the colored layer 62 so formed. Therefore, changingthe film thickness will give a different color tone or a different feelof material to the colored layer 62.

Afterward, time scales, characters, symbols and the like are formed onthe surface of the colored layer 62 depending on the need.

Since the colored layer 62 is formed of the ceramic paint containing ametal compound as a principal component, the surface is formed to berough. When the surface of the colored layer 62 is kept as rough as inthe above, the irregular reflection of light will give soft and warmcolor tones.

On the other hand, the surface of the colored layer 62 may be madesmooth with the surface roughness of about 0.05 to 0.1 μm by lapping orthe like. This will restrict the irregular reflection of light on thesurface thereof and enhance the transmittance of light. Consequently,the quantity of light reaching the solar battery 4 placed on the rearside of the dial plate 6 increases, so that the solar battery generatesmore electromotive force.

Lapping can be done by using diamond abrasive grains having a graindiameter of about 3 μm.

FIG. 4 is a sectional view showing one modified embodiment of the dialplate for a solar battery powered watch relating to the first embodimentdescribed above.

In this modified embodiment, the colored coating layer comprises thecolored layer 62 described above and an intermediate layer 63.

The substrate 61 in this modified embodiment is substantially the sameas the one described in the first embodiment, thus a detaileddescription thereof will be omitted.

The intermediate layer 63 is formed in an intermediate area between thesubstrate 61 and the colored layer 62.

This intermediate layer 63 is formed by a glass material containingsilicon such as a glaze (glaze for ceramics) used for making ceramics.

This ceramic glaze, containing silicon, is formed into a glossy glassfilm by a baking treatment.

What can be used for the ceramic glaze are materials containing naturalinorganic materials, such as feldspar, silica rock, lime stone, talc,ash, etc., and materials containing chemical materials, such as zincwhite, white lead (karatsuti), red lead, barium carbonate, soda ash,frit, etc.

These ceramic glazes are formed into the intermediate layer 63 by thebaking treatment under a high temperature of, for example, 1100 to 1300°C. The intermediate layer 63 formed on the surface of the substrate 61functions to clog fine holes on the surface of the substrate 61 formedof a ceramic material and keep the colored layer 62 from soaking intothe substrate 61.

In this modified embodiment, it is preferable to select the ceramicpaint used for forming the colored layer 62 which has a bakingtemperature sufficiently low (for example, 700 to 900° C.) compared tothat of the ceramic glazes used for forming the intermediate layer 63.

Therefore, using an overglaze paint of a low baking temperature type forthe ceramic paint will remove the risk of softening the intermediatelayer 63 formed beforehand on the surface of the substrate 61, in thebaking of the colored layer 62.

Generally, there are achromatic transparent and light-colored ceramicglazes used for forming the intermediate layer 63. Using thelight-colored ceramic glaze for forming the intermediate layer 63 willmix the color of the colored layer 62 with the color of the intermediatelayer 63 and present a still different color expression. When thetransmittance of light is needed to be kept at a high level, it ispreferable to use an achromatic transparent ceramic glaze also for thisintermediate layer 63.

The intermediate layer 63 can be formed, for example, according to thefollowing method.

After a ceramic glaze as described above is selected and dispersed inwater and churned, the glaze is applied on the surface of the substrate61 by means of the screen printing method, rolling application method,or manual operation by a writing brush or paint brush. Then, the appliedsurface is processed under a baking temperature of 1100 to 1300° C.,thus forming the intermediate layer 63. This baking treatment is done inan atmosphere of oxidation or reduction.

The thickness of the intermediate layer 63 may be adjusted to, forexample, about 5 μm to 10 μm.

This intermediate layer 63 can be formed of various glass materialsother than the ceramic glaze. For a glass material used for forming theintermediate layer 63, a high melting point glass having a bakingtemperature of, for example, 950 to 1300° C. can be used, the bakingtemperature of which is sufficiently high compared to that of theceramic paint used for forming the colored layer 62. The reason is that,if the baking temperature for the intermediate layer 63 is lower thanthat for the colored layer 62, the intermediate layer 63 will be meltedand be mutually diffused with the colored layer 62 when the coloredlayer 62 is formed.

This high melting point glass as well as a low melting point glass ismade into glass powder, which is mixed with a vehicle into a paste. Thepaste is applied by a screen printing method, writing brush, or paintbrush and baked. Ethylcellulose dissolved in a-terpineol may be used asthe vehicle.

The surface of the intermediate layer 63 may be made smooth with asurface roughness of about 0.05 to 0.1 μm by lapping or the like. Thiswill restrict the irregular reflection of light on the surface thereof(finally, the interface with the colored layer 62) and enhance thetransmittance of light. Consequently, the quantity of light reaching thesolar battery 4 placed on the rear side of the dial plate 6 increases,so that the solar battery generates more electromotive force.

Lapping can be done by using diamond abrasive grains having a graindiameter of about 3 μm.

On the contrary, barrel or honing processing can roughen the surface ofthe intermediate layer 63. In this case, the irregular reflection isstrengthened on the surface (finally, the interface with the coloredlayer 62) of the intermediate layer 63, and the transmittance of lightis decreased; however, the irregular reflection of light will presentsoft and warm color tones.

FIG. 5 is a sectional view showing another modified embodiment of a dialplate for a solar battery powered watch relating to the firstembodiment.

In this modified embodiment, the colored coating layer comprises acolored layer 62 described above, the intermediate layer 63, andadditionally a surface layer 64.

The substrate 61, colored layer 62, and intermediate layer 63 in thismodified embodiment are virtually the same as the ones described in thefirst embodiment and the modified embodiment of the same, thus adetailed description will be here omitted.

The surface layer 64 is formed on the surface of the colored layer 62,which makes the surface of the colored layer 62 glossy to enhance thecolor quality and protects the color of the colored layer 62 fromdecoloring.

This surface layer 64 can be formed of a low melting point glass such asa lead derivative or boric acid derivative that can form a glass film ata temperature (for example, 350 to 500° C.) sufficiently low compared tothe baking temperature for the overglaze paint used for forming thecolored layer 62.

First, glass powder of a low melting point is mixed with vehicleobtained by dissolving acrylic resin in a-terpineol, forming a glasspaste having a low melting point. This paste is applied on the surfaceof the colored layer 62 by a screen printing method, writing brush, orpaint brush. And then, the paste applied surface of the colored layer 62is processed in a baking temperature of 350 to 500° C.; thus forming thesurface layer 64. This baking treatment is processed in an oxidationatmosphere. The reason that the baking temperature of the surface layer64 is set to a lower temperature than that of the colored layer 62 is toprevent the pigment of the colored layer 62 from diffusing into thesurface layer 64.

Afterward, time scales, characters, symbols and the like are formed onthe surface of the surface layer 64 depending on the need.

The surface of the surface layer 64 may be made smooth with a surfaceroughness of about 0.05 to 0.1 μm by lapping or the like. This willrestrict the irregular reflection of light on the surface thereof andenhance the transmittance of light. Consequently, the quantity of lightreaching the solar battery 4 placed on the rear side of the dial plate 6increases, so that the solar battery generates more electromotive force.

Lapping can be done by using diamond abrasive grains having a graindiameter of about 3 μm.

According to the experiment made by the inventors of the presentinvention, in the dial plate where the surface of the surface layer 64is made smooth by lapping and the surface of the same is not lapped, thetransmittance of light of the former was increased by 3.5 to 5.0%.

On the contrary, barrel or honing processing can roughen the surface ofthe surface layer 64. In this case, the irregular reflection isstrengthened on the surface of the surface layer 64, and thetransmittance of light is decreased; however, the irregular reflectionof light will present soft and warm color tones.

Varying the film formation thickness of the colored layer 62,intermediate layer 63, and surface layer 64 of the dial plate 6 makesthe reflection and refraction of light not uniform, whereby variouspatterns can be formed.

In the modified embodiment described above, the intermediate layer 63and the surface layer 64 are formed by using a ceramic glaze and a lowmelting point glass, respectively; however, at least one of theintermediate layer 63 and the surface layer 64 may be formed by an oxidefilm such as a silicon oxide film (SiO₂), tantalum oxide film (Ta₂ O₅),or aluminum oxide film (Al₂ O₃).

When the foregoing oxide film is applied to the intermediate layer 63,fine holes on the surface of the substrate 61 formed of a ceramicmaterial are clogged, which prevents the colored layer 62 from soakinginto the substrate 61. When the foregoing oxide film is applied to thesurface layer 64, the surface of the colored layer 62 can be madeglossy, which enhances the color quality and protects the colored layer62 from decoloring.

These oxide films can be formed by the vacuum evaporation method,sputtering, chemical vapor deposition method and the like; the formationtemperature may reliably be lower than 300° C. in each method. The oxidefilm formed will not change at all even if it is heated to a temperaturehigher than 1000° C. However generally, with these methods it isdifficult to make the film thick, and a thickness thinner than a few μmcannot be avoided in practice; nevertheless, these oxide films have anequivalent effect to the case where a ceramic glaze or a low meltingpoint glass is used.

Second Embodiment

FIG. 6 is a sectional view showing the constitution of the dial platefor a solar battery powered watch relating to the second embodiment ofthe present invention.

The dial plate relating to this embodiment can be applied, for example,to the dial plate for the solar battery powered watch shown in FIG. 3.The surface constitution of the dial plate relating to the secondembodiment is the same as that of the dial plate of the first embodimentshown in FIG. 2.

The dial plate 6 for the solar battery powered watch relating to thesecond embodiment is characterized in that a mixed colored layer 65 as acolored coating layer is formed on the surface of the substrate 61.

The adjustment of transmittance has an important meaning for the dialplate 6 according to the second embodiment.

For example, it is preferable that the dial plate 6 has a transmittanceof light capable of transmitting 1/4 or more of the irradiated light soas to secure sufficient electric power for the solar battery 4 and tokeep a steady driving of the watch. Further, it is preferable that thedial plate of a watch provided with an additive function such as anilluminating or alarming function which consumes much power has atransmittance of light capable of transmitting 1/3 or more of theirradiated light.

Meanwhile, it is preferable that the dial plate has a transmittance oflight capable of transmitting 2/3 or less of the irradiated light toconceal the solar battery 4 (particularly the color thereof) from view.Further, if the dial plate 6 has a light color, it is preferable thatthe dial plate has a transmittance of light capable of transmitting 1/2or less of the irradiated light so as to more securely conceal the solarbattery 4 having a dark color such as dark violet.

In view of the security of the electric power and of the concealing ofthe solar battery 4, it is preferable that the transmittance of light ofthe dial plate 6 be adjusted.

As explained in the foregoing, it is preferable that the transmittanceof light of the dial plate 6 be decided based on the ratio between theamount of the electric power of the solar battery 4 generated by thelight irradiated on the solar battery 4 in a state where the dial plate6 is not inserted and that of the solar battery 4 generated by the lighttransmitted through the dial plate 6 in a state where the dial plate 6is inserted.

The constitution of the substrate 61 is the same as the one in the firstembodiment described above; therefore, the description of the same willbe omitted.

The mixed colored layer 65 is formed of a coloring material made bymixing a glass material such as a ceramic glaze and a paste of a lowmelting point glass with a ceramic paint. The ceramic glaze used in thisembodiment is the same one as used for forming the intermediate layer 63(FIG. 4, 5) in the first embodiment described above. And, the paste of alow melting point glass used herein is the same one as used for formingthe surface layer 64 (FIG. 5) in the first embodiment.

As described above, there are transparent and lightly colored ceramicglazes; both of them may be used in this embodiment.

When a lightly colored ceramic glaze is used, it can be mixed with aceramic paint, expanding color variation. On the other hand, when anachromatic transparent ceramic glaze is used, the transmittance of lightis enhanced.

When the ceramic paint mixed with the ceramic glaze is used, anunderglaze paint must be used which has a baking temperature equivalentor very close to the baking temperature for the ceramic glaze (forexample, 1100 to 1300° C.). The reason is that obtaining a sufficientfunction of the glaze and the paint is impossible if the bakingtemperature is different with the ceramic glaze and the ceramic paintwhich are processed integrally simultaneously.

On the other hand, when the ceramic paint is used being mixed with apaste of a low melting point glass, it is preferable to use an overglazepaint having a low baking temperature of 700 to 900° C. as the ceramicpaint and select the paste of a low melting point glass having virtuallythe same baking temperature. The paste of a low melting point glass inthis embodiment is slightly different in composition from the one havinga still lower baking temperature which is used in the first embodiment.

The ceramic paint used in this second embodiment also exertssubstantially the same effect when it is used by the similar method tothe one used in the foregoing first embodiment.

The ceramic paint used in the second embodiment is a paint formed insuch a manner that a metal oxide as the metal compound is dispersed intowater or oil and the viscosity is adjusted by using funori or the like,or a liquid pigment paint in which water-soluble metallic chloride asthe metal compound is dissolved into water; different kinds of metalcompound used produce different colors.

Using cobalt chloride or cobalt nitrate as the metal compound for theliquid pigment paint will produce a blue ceramic paint. Using ironchloride or iron sulfate will produce a yellow ceramic paint. Usingferric chloride or copper sulfate will produce a green ceramic paint.Using chromium sulfate or chromium nitrate will produce a brown ceramicpaint. Using gold chloride will produce a pink ceramic paint.

Thus, selection of the kind of the metal compound will present variouscolors needed for designing the dial plate 6 for the watch.

Further, mixing several kinds of metal compounds described above in anappropriate ratio will produce a ceramic paint of different tone.

Mixing, for example, metal oxides of cobalt and chrome will produce agreen spectrum ceramic paint. Mixing metal oxides of cobalt andmanganese will produce a blue spectrum ceramic paint. Mixing metaloxides of gold and cobalt will produce a red-purple spectrum ceramicpaint.

The mixed colored layer 65 is formed with a film thickness of about 20to 30 μm. The transmittance of light can appropriately be adjusted byadjusting the film thickness.

Next, the method of manufacturing the dial plate 6 relating to thesecond embodiment will be described. The method of manufacturing thedial plate 6 can be divided into the method of manufacturing thesubstrate 61 and the formation of the mixed colored layer 65. The methodof manufacturing the substrate 61 is just the same as the one in thefirst embodiment described above. Therefore herein, the description willbe omitted.

The mixed colored layer 65 can be formed as follows.

First, a mixed coloring material is fabricated by mixing a ceramic paintwith a ceramic glaze. A concrete manufacturing method will be presentedherein which the inventors executed.

A metal oxide is dispersed in water and kneaded, which is processed in aheating treatment to evaporate moisture; after further being mixed, apowdery ceramic paint is made for use. A powdery ceramic glaze availablein market was employed.

A mixed coloring material is fabricated in such a manner that a powderyceramic paint and ceramic glaze are mixed in an appropriate ratio (forexample, 1 to 5 in weight) and are well kneaded with oil added.

It is preferable to adjust the additive quantity of oil in considerationfor the film thickness of the mixed colored layer 65 formed by thescreen printing method and the screen printability.

Adjusting the quantity of oil added enhances the screen printability,whereby the film thickness of the mixed colored layer 65 becomes uniformand the periphery of the mixed colored layer 65 assumes a deep color.

This mixed coloring material is applied on the substrate 61 by thescreen printing method. The film thickness of the mixed coloringmaterial is adjusted to about 20 to 30 μm. The screen for use in thescreen printing is selected out of 150 mesh to 200 mesh.

When the film thickness of the mixed coloring material is not adjustedto a desired one at the first screen printing, repeated application forseveral times is recommended.

Next, the baking treatment under a temperature of 1100 to 1300° C. isexecuted and the mixed colored layer 65 is formed. This treatment isexecuted in an atmosphere of oxidation or reduction.

Next, time scales, characters, and symbols are formed depending on theneed.

The surface of the mixed colored layer 65 is made smooth with a surfaceroughness of about 0.05 to 0.1 μm by lapping or the like, whichrestricts the irregular reflection on the surface thereof and enhancesthe transmittance of light.

According to the comparison made by the inventors of the presentinvention, between the dial plate 6 where the surface of the mixedcolored layer 65 is lapped and the surface of the same is not lapped,the transmittance of light of the former was increased by 3.0 to 5.0%.

Lapping the surface of the mixed colored layer 65 may be done by usingdiamond abrasive grains having a grain diameter of about 3 to 5 μm.

When the surface of the mixed colored layer 65 is lapped by usingdiamond abrasive grains, lapping the substrate 61 on the rear side isalso preferable.

There is a possibility in lapping the mixed colored layer 65 thatdiamond abrasive grains and lapping residues are attached on the rearsurface of the substrate 61, which can appear as contamination. Toprevent this from occurring, lapping the substrate 61 on the rearsurface to make it flat and smooth is effective in keeping the diamondabrasive grains and lapping residues from attaching thereon, thus makingthe surface difficult to be contaminated.

According to the comparison made by the inventors of the presentinvention, between the dial plate 6 where the rear surface of thesubstrate 61 is lapped and the rear surface of the same is not lapped,the transmittance of light of the former was increased by 1.5 to 2.5%.Lapping on the rear side of the substrate 61 is identically applicableas in the first embodiment.

When the contamination on the rear surface of the substrate 61 becomesapparent, baking the dial plate 6 under a temperature of 700 to 1000° C.and burning off the diamond abrasive grains and lapping residues may beperformed to keep the surface clean. In this case, the bakingtemperature needs to be lower than the baking temperature for formingthe colored coating layer.

The baking treatment for cleaning is performed in an atmosphere ofoxidation or reduction. This baking treatment is also identicallyapplicable to others except the one (FIG. 5) used for the surface layer64 in the first embodiment.

On the other hand, barrel or honing processing can roughen the surfaceof the mixed colored layer 65. In this case, the irregular reflection isstrengthened on the surface of the mixed colored layer 65, and thetransmittance of light is decreased; however, the irregular reflectionof light will present soft and warm color tones.

Raising the baking temperature of the mixed colored layer 65 to atemperature higher than the standard setting temperature will boil theceramic glaze and low melting point glass, by which a fine pattern canbe formed on the surface.

FIG. 7 is a sectional view showing a modified embodiment of the dialplate for the solar battery powered watch relating to the foregoingsecond embodiment.

In this modified embodiment, the colored coating layer comprises themixed colored layer 65 described above and the surface layer 64.

The substrate 61 and the mixed colored layer 65 in this modifiedembodiment are substantially the same as the ones described above in thesecond embodiment; therefore, a detailed description will be omitted.

The surface layer 64 can be formed of a low melting point glass in thesame manner as the surface layer 64 (FIG. 5) formed on the surface ofthe colored layer 62 in the modified embodiment to the first embodiment.This surface layer 64 is formed with a film thickness of about 20 to 30μm. For the low melting point glass used for the surface layer 64, onehaving a baking temperature sufficiently lower than that for the mixedcolored layer 65 is selected, so that the surface layer 64 and the mixedcolored layer 65 will not mutually diffuse.

Usually, the low melting point glass is transparent; adding a smallquantity of pigment assumes a light color, with which ceramic paint ismixed to add a new color variation. On the other hand, when anachromatic low melting point glass is used, the transmittance of lightcan be increased.

It is preferable that the dial plate 6 has a transmittance of lightcapable of transmitting 1/4 or more of the irradiated light so as tosecure sufficient electric power for the solar battery 4 and to keep asteady driving of the watch. Further, it is preferable that the dialplate of a watch provided with an additive function such as anilluminating or alarming function which consumes much power has atransmittance of light capable of transmitting 1/3 or more of theirradiated light.

Meanwhile, it is preferable that the dial plate has a transmittance oflight capable of transmitting 2/3 or less of the irradiated light toconceal the solar battery 4 (particularly the color thereof) from view.Further, if the dial plate 6 has a light color, it is preferable thatthe dial plate has a transmittance of light capable of transmitting 1/2or less of the irradiated light so as to more securely conceal the solarbattery 4 having a dark color such as dark violet.

In view of the security of the electric power and of the concealing ofthe solar battery 4, it is preferable that the transmittance of light ofthe dial plate 6 be adjusted.

As explained in the foregoing, it is preferable that the transmittanceof light of the dial plate 6 be decided based on the ratio between theamount of electric power of the solar battery 4 generated by the lightirradiated on the solar battery 4 in a state where the dial plate 6 isnot inserted and that of the solar battery 4 generated by the lighttransmitted through the dial plate 6 in a state where the dial plate 6is inserted.

The surface layer 64 can be formed on the surface of the mixed coloredlayer 65 by the following method.

First, a glass powder of a low melting point such as a lead derivativeor boric acid derivative is prepared which can form a glass film at atemperature (for example, 350 to 500° C.) sufficiently lower than thebaking temperature for the mixed colored layer 62. And, this glasspowder is kneaded with a vehicle obtained by dissolving acrylic resin ina-terpineol. The quantity of the vehicle added is preferably adjusted inconsideration for the film thickness of the surface layer 64 formed bythe screen printing method and the screen printability.

The glass paste of a low melting point thus adjusted is applied on thesurface of the mixed colored layer 65 by the screen printing method. Thefilm thickness of a low melting point glass is adjusted to about 20 to30 μm. And, the screen used for the screen printing is about 150 to 200mesh.

When the film thickness of a low melting point glass is not adjusted toa desired one at the first screen printing, repeated application forseveral times is recommended.

And then, a baking treatment is processed under the temperature of 350to 500° C.; thus forming the surface layer 64. This baking treatment maybe processed in an oxidation atmosphere.

Afterward, time scales, characters, symbols and the like are formed onthe surface of the surface layer 64 depending on the need.

Lapping the surface of the surface layer 64 will produce a smoothsurface with a surface roughness of about 0.05 to 0.1 μm; thus theirregular reflection on the surface can be reduced and the transmittanceof light will be increased.

The inventor of the present invention made two types of dial plates 6,one where the surface of the surface layer 64 was made smooth bylapping, and another where the surface was not lapped, and compared thetransmittance of light between these two types. It was found that thetransmittance of light of the former was increased by 3.0 to 5.0%.

Lapping the surface of a surface layer 64 may be done by using diamondabrasive grains having a grain diameter of about 3 to 5 μm.

When the surface of the surface layer 64 is lapped by using diamondabrasive grains, lapping the substrate 61 on the rear side is alsopreferable.

There is a possibility in lapping the surface layer 64 that diamondabrasive grains and lapping residues are attached on the rear surface ofthe substrate 61, which can appear as contamination. To prevent thisfrom occurring, lapping the substrate 61 on the rear surface to make itflat and smooth is effective in keeping the diamond abrasive grains andlapping residues from attaching thereon, thus making the surfacedifficult to contaminate.

According to the comparison made by the inventors of the presentinvention, between the dial plate 6 where the rear surface of thesubstrate 61 is lapped and the rear surface of the same is not lapped,the transmittance of light of the former was increased by 1.5 to 2.5%.

On the other hand, barrel or honing processing can roughen the surfaceof the surface layer 64. In this case, the irregular reflection isstrengthened on the surface of the surface layer 64, and thetransmittance of light is decreased; however, the irregular reflectionof light will present soft and warm color tones.

Varying the film thickness formed of the mixed colored layer 65 andsurface layer 64 of the dial plate 6 makes the reflection and refractionof light not uniform, whereby various patterns can be formed.

In the modified embodiment described above, the surface layer 64 wasformed by using glass of a low melting point; however, the surface layer64 may be formed by an oxide film such as a silicon oxide film (SiO₂),tantalum oxide film (Ta₂ O₅), or aluminum oxide film (Al₂ O₃).

These oxide films can be formed by the vacuum evaporation method,sputtering, chemical vapor deposition method or the like; the formationtemperature may reliably be lower than 300° C. in each method. The oxidefilm formed will not change at all even if it is heated to a temperaturehigher than 1000° C. However generally, with these methods it isdifficult to make the film thick, and the thickness thinner than a fewμm cannot be avoided in practice; nevertheless, these oxide films havean equivalent effect to the case where a ceramic glaze or glass of a lowmelting point is used.

Third Embodiment

FIG. 8 is a plan view showing an example of the surface constitution ofthe dial plate for the solar battery powered watch relating to the thirdembodiment of the present invention.

Dial plates for solar battery powered watches have regions (additivefunctional regions) for various additive functions such as timeindication function for the 24 hour system, a date indication function,a day indication function, a stopwatch function, and time-differenceindication function.

In FIG. 8, for example, 106a is an additive functional region forindicating the month of the year, 106b is an additive functional regionfor indicating the date of the month, and 106c is an additive functionalregion for indicating the day of the week.

Differentiating the color tone for the additive functional regions,106a, 106b, 106c from the other region 206 (non-additive functionalregion) on the surface of the dial plate 6 makes the additive functionalregions easy to view, enhances functionability, and presents novelty indesign appearance.

In the dial plate 6 of the third embodiment, the additive functionalregions, 106a, 106b, 106c bear a construction so as to differentiatetheir color tone from the other additive functional region 206 so as toobtain the above-mentioned effect.

In the dial plate 6 of the third embodiment, as shown in FIG. 9, thesurface for the additive functional region 106 (representative referencesymbol for 106a, 106b, 106c) is formed in a recessed shape so that thethickness of the region is thinner compared to the non-additivefunctional region 206.

The constitutional materials and the manufacturing method of thesubstrate 61 may be the same as the ones in the first embodimentdescribed above. However, a metal mold is needed to form the recessedshape for the additive functional region 106 shown in FIG. 8, and toform a throughhole 6d to accommodate a drive shaft for an auxiliary hand(for date, day, etc.) depending on the need.

It is preferable that the dial plate 6 formed of the substrate 61 has atransmittance of light capable of transmitting 1/4 or more of theirradiated light so as to secure sufficient electric power for the solarbattery 4 and to keep a steady driving of the watch. Further, it ispreferable that the dial plate of a watch provided with an additivefunction such as an illuminating or alarming function for consuming muchpower has a transmittance of light capable of transmitting 1/3 or moreof the irradiated light.

Meanwhile, it is preferable that the dial plate has a transmittance oflight capable of transmitting 2/3 or less of the irradiated light toconceal the solar battery 4 (particularly the color thereof) from view.Further, if the dial plate 6 has a light color, it is preferable thatthe dial plate has a transmittance of light capable of transmitting 1/2or less of the irradiated light so as to more securely conceal the solarbattery 4 having a dark color such as dark violet.

In view of the security of the electric power and of the concealing ofthe solar battery 4, it is preferable that the transmittance of light ofthe dial plate 6 be adjusted.

As explained in the foregoing, it is preferable that the transmittanceof light of the dial plate 6 be decided based on the ratio between theamount of electric power of the solar battery 4 generated by the lightirradiated on the solar battery 4 in a state where the dial plate 6 isnot inserted and that of the solar battery 4 generated by the lighttransmitted through the dial plate 6 in a state where the dial plate 6is inserted.

The dimension of thickness of the substrate 61 is adjusted appropriatelyin consideration for the strength and for the transmittance of light.That is, the strength must be enough to withstand the usage for the dialplate of a watch and the transmittance is adjusted so as to securelytransmit about 1/3 to 2/3 of the quantity of incident light.

To form the additive functional region 106 and the non-additivefunctional region 206 in different thickness differentiates thetransmittance and diffusivity of incident light on the substrate 61formed of a ceramic material in the additive functional region 106 fromthose in the non-additive functional region 206. Consequently, both theregions 106, 206 assume different color tones.

Ambient light incident on the dial plate 6 irregularly reflects on thesurface and inside of the dial plate 61, a portion of which comes out ofthe dial plate 6 as reflected light. On the other hand, as shown in FIG.3, a colored solar battery 4 (usually, red-purple) is placed on the rearside of the dial plate 6. Light transmitted through the dial plate 6 ofthe ambient light incident on the dial plate 6 is reflected on the solarbattery 4, which falls on the dial plate 6 from the back side, coloredby the solar battery 4. A portion of the colored light falling on thedial plate 6 from the back side is reflected and the other portiontransmits diffusedly through to the front surface of the dial plate 6.The transmittance and the reflection coefficient of light which aregiven by a series of transmissions and reflections through the dialplate 6 depend on the thickness of the dial plate 6 (namely, thesubstrate 61) and the diffusivity of light, and the additive functionalregion 106 having a thinner thickness bears a higher transmittance oflight. Consequently, the additive functional region 106 and thenon-additive functional region 206 assume different color tones.

When the substrate 61 is formed of a milky white ceramic material, thethicker non-additive functional region 206 reflects more surroundingincident light. This reflection light is white. When the lighttransmitted through the region 206 and reflected on the solar battery 4again is transmitted through the region 206 to the front surface, thequantity of light becomes minute. Therefore, the non-additive functionalregion 206 assumes a milky white appearance.

On the other hand, since the transmission of colored light increases inthe thinner functional region 106, the milky white of the substrate 61and the red-purple of the solar battery 4 are mixed to assume a graycolor.

Further, the thickness of the functional region 106 in the substrate 61can be made thinner by forming a recessed part on the back side thereof.Forming a recessed part on the front or back surface of the non-additivefunctional region 206 to make the thickness thinner than that of theadditive functional region 106 will also assume different color tones ineach region.

Fourth Embodiment

FIGS. 10 to 13 are sectional views showing the constitution of the dialplate for a solar battery powered watch relating to the fourthembodiment of the present invention.

The dial plate relating to this embodiment can also be applied to thedial plate 6 for the solar battery powered watch having, for example,the additive functional regions 106a, 106b, 106c shown in FIG. 8.

In the dial plate 6 for the solar battery powered watch relating to thefourth embodiment, a colored coating layer is formed on the bottom ofthe recessed part formed in the additive functional regions 106, wherebythe additive functional regions 106 and the non-additive functionalregion 206 differ in color.

The dial plate 6 shown in FIG. 10, for example, has the colored layer 62as a colored coating layer formed on the bottom of a recessed partformed in the additive functional region 106.

This colored layer 62 can be formed by using a ceramic paint in the samemanner as forming the colored layer 62 in the first embodiment describedabove. In this case, since only the colored layer 62 is formed by theceramic paint in the additive functional region 106, the bakingtemperature of the ceramic paint is not a factor.

When the colored layer 62 is formed directly on the surface of thesubstrate 61, the ceramic paint may soak into the substrate 61 to blurthe circumferential edges. In order to prevent the cicumferential edgesfrom being blurred, as shown in FIG. 11, the intermediate layer 63 maybe formed between the substrate 61 and the colored layer 62 so as toform a colored coating layer with the colored layer 62 and theintermediate layer 63.

The intermediate layer 63 may be formed using a glass material such as aceramic glaze in the same manner as the intermediate layer 63 in themodified embodiment to the first embodiment described above.

When the intermediate layer 63 is formed, in the same manner as thefirst embodiment, the ceramic paint for the colored layer 62 is usedwhich has a lower baking temperature than that of the glass material ofthe intermediate layer 63.

And, for a replacement of the colored layer 62 shown in FIG. 10, themixed colored layer 65 in the second embodiment described above may beformed as a colored coating layer, in the additive functional region 106of the dial plate 6.

The mixed colored layer 65 is formed by a mixed coloring material whichis formed by mixing a glass material such as a ceramic glaze or a lowmelting point glass with a ceramic paint. The adjustment of the mixedcoloring material and the formation of the mixed colored layer 65 may beexecuted by the same method as in the second embodiment.

The ceramic paint is used which has a baking temperature virtually equalto that of a glass material such as a ceramic glaze or a low meltingpoint glass.

In the dial plate 6 shown in FIG. 12, a surface layer 64 is furtherformed on the surface of the colored layer 62 or the mixed colored layer65 formed in the additive functional region 106, whereby the coatinglayer comprises the colored layer 62 or the mixed colored layer 65 andthe surface layer 64. The surface layer 64 can be formed by usingvirtually the same material and method as the ones used for forming thesurface layer 64 in the modified embodiment to the first and secondembodiment.

And, in the dial plate shown in FIG. 13, the intermediate layer 63, thecolored layer 62, and the surface layer 64 are formed as a coloredcoating layer, on the bottom of the recessed part formed in the additivefunctional region 106. The constitution and formation method of theintermediate layer 63, the colored layer 62, and the surface layer 64are virtually the same as those of the intermediate layer 63, thecolored layer 62, and the surface layer 64 in the first embodiment andits modified embodiment described above.

Forming a colored coating layer in the additive functional region 106,as mentioned above, will assume different color tones in the additivefunctional region 106 and the non-additive functional region 206.

Further, in the above-mentioned constitution, the colored coating layeris formed on the bottom of the recessed part formed in the additivefunctional region 106; however on the contrary, the colored coatinglayer may be formed in the non-additive functional region 206. And,different colored coating layers may be formed each in the additivefunctional region 106 and the non-additive functional region 206 todifferentiate the color tone in each region.

In a recessed part formed in the non-additive functional region 206, andalso in a recessed part formed on the back surface of the substrate 61,corresponding to the additive functional region 106 or the non-additivefunctional region 206, the color tone in each region can bedifferentiated by the combination of the foregoing coating layer.

Fifth Embodiment

FIGS. 14 to 17 are sectional views showing the constitution of the dialplate for a solar battery powered watch relating to the fifth embodimentof the present invention.

The dial plate relating to this embodiment can also be applied to thedial plate 6 for the solar battery powered watch having, for example,the additive functional regions 106a, 106b, 106c shown in FIG. 8.

The dial plate 6 for the solar battery powered watch relating to thefifth embodiment does not form a recessed part on the front or backsurface of the substrate 61, but flattens these surfaces. And, coloredcoating layers are formed with different color tones so as todifferentiate the additive functional region 106 from the non-additivefunctional region 206.

In the dial plate 6 shown in FIG. 14, for example, two colored layers62, 62' in different colors are formed as the coating layer, on portionsof regions corresponding to the additive functional region 106 and thenon-additive functional region 206.

These colored layers 62, 62' can be formed using the ceramic paint inthe same manner as the colored layer 62 in the first embodimentdescribed above. In this case, only the colored layers 62, 62' formed ofceramic paints are formed on the surface of the substrate 61, and hence,the baking temperature of ceramic paints is not a factor.

When the colored layers 62, 62' are directly formed on the surface ofthe substrate 61, the ceramic paint may be soaked into the substrate 61to blur the circumferential edges as described above. In order to avoidthe color of the circumferential edges from being blurred, as shown inFIG. 15, intermediate layers 63, 63' may be formed in the substrate 61and below the colored layers 62, 62' so as to form colored coatinglayers with the colored layers 62, 62' and the intermediate layers 63,63'.

The intermediate layers 63, 63' may be formed by using ceramic glazes inthe same manner as the intermediate layer 63 in the modified embodimentto the first embodiment. The intermediate layer 63 and 63' may be formedof same type of material or different types of material.

When the intermediate layers 63, 63' are formed, the ceramic paints forthe colored layers 62, 62', are used which have lower bakingtemperatures than those of the ceramic glazes for the intermediatelayers 63, 63'.

And, for the replacement of the colored layers 62, 62' shown in FIG. 14,the mixed colored layers 65, 65' in the second embodiment describedabove may be formed as colored coating layers, in the additivefunctional region 106 and in the non-additive functional region.

Differentiating the color of the mixed colored layer 65 formed in theadditive functional region 106 from the color of the mixed colored layer65' formed in the non-additive functional region 206, varies the colortone in each region.

The mixed colored layers 65, 65' can be formed by a mixed coloringmaterial which is formed by mixing a glass material such as a ceramicglaze or a low melting point glass with a ceramic paint. The adjustmentof the mixed coloring material and the formation of the mixed coloredlayers 65, 65' may be executed by the same method as in the secondembodiment described above.

The ceramic paint is used which has a baking temperature virtually equalto that of a glass material such as a ceramic glaze or a low meltingpoint glass.

In the dial plate 6 shown in FIG. 16, surface layers 64, 64' are furtherformed on the surface of the colored layers 62, 62' or the mixed coloredlayers 65, 65', each of which has a different color and is formed on thesubstrate 61, whereby the coating layer comprises the colored layers 62,62' or the mixed colored layers 65, 65' and the surface layers 64, 64'.

The surface layers 64, 64' can be formed by using virtually the samematerial and method as the ones used for forming the surface layer 64 inthe modified embodiment to the first and second embodiment.

And, in the dial plate 6 shown in FIG. 17, colored coating layers areformed on the surface of the base plate 61, which comprise theintermediate layers 63, 63', the colored layers 62, 62', and the surfacelayers 64, 64'. The colored layer 62 formed in the additive functionalregion 106 and the colored layer 62' formed in the non-additivefunctional region 206 are formed by the ceramic paints in differentcolors.

The constitution and formation method of the intermediate layers 63,63', the colored layers 62, 62,' and the surface layers 64, 64' arevirtually the same as those of the intermediate layer 63, the coloredlayer 62, and the surface layer 64 in the first embodiment and itsmodified embodiment described above.

Forming colored coating layers in different colors in the additivefunctional layer 106, and the non-additive functional region 206, asmentioned above, will differentiate the additive functional region 106from the non-additive functional region 206.

Further, in the abovementioned constitution, the colored coating layersare formed on the surface of the substrate 61, however different coloredcoating layers can be formed each in the additive functional region 106and the non-additive functional region 206 to differentiate the colortone in each region.

And, forming a colored coating layer in either the additive functionalregion 106 or the non-additive functional region 206 will presentdifferent color tones to both the regions.

Furthermore, forming the colored coating layer of the additivefunctional region 106 and non-additive functional region 206 separatelyon the front and back surface of the substrate 61 can differentiate thecolor tones for each region.

Lapping the front or back surface of the substrate 61 will produce asmooth surface with a surface roughness of about 0.05 to 0.1 μm; thusthe irregular reflection on the surface can be reduced and thetransmittance of light will be enhanced. Particularly when the coloredlayers 62, 62' are formed directly on the substrate 61, lapping thesurface of the substrate 61 for forming the colored layers thereon willkeep the ceramic paint from soaking into.

Further, after forming the colored layers 62, 62' and the mixed coloredlayers 65, 65', irregularly lapping or grinding these surfaces 62, 62'or 65, 65' will form patterns thereon and change the color tones.

When forming colored layers in more than two layers, varying the formingthickness of each layer in the dial plate 6 causes the reflection andrefraction of light to be uneven and makes various patterns.

INDUSTRIAL UTILIZATION

The present invention can apply to a dial plate for a solar batterypowered watch which operates using the solar battery as an energysource, and it can conceal the solar battery from view and satisfy thevarious tastes of purchasers by the various possible color variations.

What is claimed is:
 1. A dial plate for a solar battery powered watchprovided with a solar battery, to be disposed on the front side of thesolar battery, comprising:a substrate formed of a ceramic material; anda colored coating layer formed on a front surface of the substrate,wherein the colored coating layer has a colored layer formed of aceramic paint containing a metal compound as a principal component.
 2. Adial plate for a solar battery powered watch as claimed in claim 1,wherein the colored coating layer has an intermediate layer which isformed of either a glass film or a metal oxide film, between the coloredlayer and the substrate.
 3. A dial plate for a solar battery poweredwatch as claimed in claim 2, wherein the colored coating layer has asurface layer which is formed of either a glass film or a metal oxidefilm, on the surface of the colored layer.
 4. A dial plate for a solarbattery powered watch as claimed in claim 3, wherein the front surfaceof the substrate is a flat surface made smooth by lapping.
 5. A dialplate for a solar battery powered watch as claimed in claim 3, whereinthe front surface of the substrate is a rough surface.
 6. A dial platefor a solar battery powered watch as claimed in claim 3, wherein asurface of the surface layer is a flat surface made smooth by lapping.7. A dial plate for a solar battery powered watch as claimed in claim 3,wherein a surface of the surface layer is a rough surface.
 8. A dialplate for a solar battery powered watch provided with a solar battery,to be disposed on a front side of the solar battery, comprising:asubstrate formed of a ceramic material; and a colored coating layerformed on a front surface of the substrate, wherein the colored coatinglayer has a mixed colored layer formed by a coloring material mixed withone of a glass material or an oxide material and a ceramic paintcontaining a metal compound as a principal component.
 9. A dial platefor a solar battery powered watch as claimed in claim 8, wherein thefront surface of the substrate is a flat surface made smooth by lapping.10. A dial plate for a solar battery powered watch as claimed in claim8, wherein the front surface of the substrate is a rough surface.
 11. Adial plate for a solar battery powered watch as claimed in claim 8,wherein a surface of the mixed colored layer is a flat surface madesmooth by lapping.
 12. A dial plate for a solar battery powered watch asclaimed in claim 8, wherein a surface of the mixed colored layer is arough surface.
 13. A dial plate for a solar battery powered watch asclaimed in claim 8, wherein the colored coating layer has a surfacelayer which is formed of either a glass film or a metal oxide film, on asurface of the mixed colored layer.
 14. A dial plate for a solar batterypowered watch as claimed in claim 13, wherein a surface of the surfacelayer is a flat surface made smooth by lapping.
 15. A dial plate for asolar battery powered watch as claimed in claim 13, wherein a surface ofthe surface layer is a rough surface.
 16. A dial plate for a solarbattery powered watch as claimed in claim 14, wherein a back surface ofthe substrate is a flat surface made smooth by lapping.
 17. A dial platefor a solar battery powered watch provided with a solar battery,disposed on a front side of the solar battery, said dial plate havingpredetermined additive functional regions and a non-additive functionalregion on a front surface thereof, comprising:a substrate which isformed of a ceramic material and provided with said additive andnon-additive functional regions wherein said additive and non-additivefunctional regions differ in thickness from each other.
 18. A dial platefor a solar battery powered watch as claimed in claim 17, wherein acolored layer formed of a coloring material containing at least aceramic coloring paint containing a metal compound as a principalcomponent is formed on at least either the additive functional regionsor non-additive functional region formed on the substrate.
 19. A dialplate for a solar battery powered watch as claimed in claim 18, whereinan intermediate layer formed of either a glass film or an oxide film isformed between the colored layer and the substrate.
 20. A dial plate fora solar battery powered watch as claimed in claim 19, wherein a surfacelayer formed of either a glass film or an oxide film is formed on asurface of the colored layer.
 21. A dial plate for a solar batterypowered watch provided with a solar battery, disposed on the front sideof the solar battery, said dial plate having predetermined additivefunctional regions and a non-additive functional region on a frontsurface thereof, comprising:a substrate which is formed of a ceramicmaterial and provided with said additive and non-additive functionalregions, wherein on at least one of said additive or non-additivefunctional regions a colored layer is formed of a coloring materialcontaining at least a ceramic paint containing a metal compound as aprincipal component.
 22. A dial plate for a solar battery powered watchas claimed in claim 21, wherein an intermediate layer formed of a glassfilm or an oxide film is formed between the colored layer and thesubstrate.
 23. A dial plate for a solar battery powered watch as claimedin claim 22, wherein a surface layer formed of a glass film or an oxidefilm is formed on a surface of the colored layer.